Key takeaways
- Step 1 — Reach level 25 and finish Lab Rat parts 1–3. The reason to do this before anything else is that the fusion slot physically refuses the recipe until part 3 is flagged complete; players who build the Lab early still cannot insert materials.
- Step 2 — Build the Lab and push it to level 3. Level 2 costs 25,000 Coins + 30 Iron Scrap; level 3 costs 60,000 Coins + 75 Iron Scrap + 1 Alchemy Core. The reason is not cosmetic: fusion success sits at 50% at Lab level 2 and rises to 70% at level 3, so every fusion you run below level 3 is a coin flip on a Mythic-tier seed.
- Step 3 — Farm the three materials. Golden Brainrot Seed drops from Alchemy Raid on Hard at wave 40+, listed at roughly 4% per clear; Alchemy Essence is guaranteed once per raid clear that reaches wave 20; Rainbow Sprout comes from the Rainbow Crate at about 12% or from the Lab vendor for 2,500 Coins with a 6-hour restock. Farming essence first is the efficient order because it is deterministic — you cannot get unlucky on a guaranteed drop.
- Step 4 — Buy an Alchemy Catalyst if you have the shards. The catalyst costs 400 Sun Shards, is single-use, and takes fusion from 70% to 100%. The reasoning is arithmetic: a failed fusion consumes the Golden Brainrot Seed, which at a 4% drop rate represents roughly 17 raid clears of expected farming, so 400 shards is cheap insurance against a 30% loss.
- Step 5 — Run the fusion, then collect from Lab storage. Rewards land in Lab storage rather than your main inventory, and a full inventory silently redirects the unit into storage overflow. Open Lab → Storage and claim from there before assuming anything failed.
Caylus is a Mythic-tier support unit in Plants vs Brainrots, and the dependable way to get it is the Alchemy Lab fusion recipe: 1× Golden Brainrot Seed, 3× Alchemy Essence, 1× Rainbow Sprout and a 250 Sun Shard crafting fee, unlocked after you finish the three-part Lab Rat questline at account level 25. The only other route is the Mythic Seed Crate, which lists a 0.75% Caylus rate per 250-shard pull — that is roughly 93 pulls for a coin-flip chance and about 306 pulls for a 90% chance. Below is the full route with prerequisites, costs, drop rates, and the fixes for the cases where the fusion completes but Caylus never lands in your inventory.
What Caylus is, and why the route changes between updates
Per its in-game Index entry, Caylus is a Mythic support plant that buffs adjacent units rather than dealing damage itself, which is why it is usually wanted for endless and raid builds instead of early-game clearing. That matters for the unlock route: because Caylus is a support Mythic rather than a headline damage unit, the developers have moved it between the Lab fusion table and the Mythic Seed Crate pool across several patches. According to the game’s official patch notes, the current version keeps it in both, but the crate pool rotates, so the crate is only a Caylus source during weeks when the Mythic pool includes it.
Practical consequence: check the Index entry first. If the “Obtained via” line under Caylus says Alchemy Lab, use the fusion route. If it says Mythic Seed Crate, the fusion recipe has been retired for that patch and you should not farm Golden Brainrot Seeds for nothing.
Prerequisites before you spend anything
| Requirement | Value | Where to check |
|---|---|---|
| Account level | 25 | Profile card, top-left of the HUD |
| Questline | Lab Rat, parts 1–3 complete | Quest board → Lab tab |
| Alchemy Lab built | 15,000 Coins + 25 Iron Scrap | Build menu |
| Lab level | 3 (fusion slot unlocks here) | Lab → Upgrade |
| Mythic owned | At least 1 in the Index | Index → Mythic tab |
| Event state | Alchemy season active, or Lab in permanent mode | News panel |
If the Lab upgrade button is greyed out with no tooltip, the usual cause is the questline rather than the level — the level gate and the quest gate are separate checks and the UI only surfaces one of them at a time.
Step-by-step: the current unlock route
- Step 1 — Reach level 25 and finish Lab Rat parts 1–3. The reason to do this before anything else is that the fusion slot physically refuses the recipe until part 3 is flagged complete; players who build the Lab early still cannot insert materials.
- Step 2 — Build the Lab and push it to level 3. Level 2 costs 25,000 Coins + 30 Iron Scrap; level 3 costs 60,000 Coins + 75 Iron Scrap + 1 Alchemy Core. The reason is not cosmetic: fusion success sits at 50% at Lab level 2 and rises to 70% at level 3, so every fusion you run below level 3 is a coin flip on a Mythic-tier seed.
- Step 3 — Farm the three materials. Golden Brainrot Seed drops from Alchemy Raid on Hard at wave 40+, listed at roughly 4% per clear; Alchemy Essence is guaranteed once per raid clear that reaches wave 20; Rainbow Sprout comes from the Rainbow Crate at about 12% or from the Lab vendor for 2,500 Coins with a 6-hour restock. Farming essence first is the efficient order because it is deterministic — you cannot get unlucky on a guaranteed drop.
- Step 4 — Buy an Alchemy Catalyst if you have the shards. The catalyst costs 400 Sun Shards, is single-use, and takes fusion from 70% to 100%. The reasoning is arithmetic: a failed fusion consumes the Golden Brainrot Seed, which at a 4% drop rate represents roughly 17 raid clears of expected farming, so 400 shards is cheap insurance against a 30% loss.
- Step 5 — Run the fusion, then collect from Lab storage. Rewards land in Lab storage rather than your main inventory, and a full inventory silently redirects the unit into storage overflow. Open Lab → Storage and claim from there before assuming anything failed.
The two routes side by side
| Route | Cost per attempt | Success chance | Attempts for 50% odds | Attempts for 90% odds | Caylus guaranteed? |
|---|---|---|---|---|---|
| Lab fusion, no catalyst | 250 Sun Shards + materials | 70% | 1 | 2 | No |
| Lab fusion, with catalyst | 650 Sun Shards + materials | 100% | 1 | 1 | Yes |
| Mythic Seed Crate | 250 Sun Shards | 0.75% | 93 | 306 | No — pity pays a random Mythic at 200 |
| Player trading | Market rate in Coins or Mythics | — | — | — | Yes, if you hold the currency |
How many attempts you actually need (the math)
Crate odds are multiplicative, not additive, so the number of pulls needed is P(at least one) = 1 − (1 − p)n. With p = 0.0075, the pull count for a 50% chance is ln(0.5) ÷ ln(0.9925) ≈ 93 pulls, and the count for a 90% chance is ln(0.1) ÷ ln(0.9925) ≈ 306 pulls. At 250 Sun Shards per pull, 306 pulls is 76,500 Sun Shards. If you farm roughly 1,800–2,400 shards per hour on Hard raid with full wave clears — a range community trackers report and that shifts with your squad — that is somewhere between 32 and 43 hours of raiding for a 90% shot at Caylus.
The same formula applied to the seed drop is why the fusion route wins for most accounts: at a 4% drop rate, the Golden Brainrot Seed needs about 17 clears for a coin-flip chance and about 57 clears for near-certainty. Compare 57 clears of deterministic farming, plus 650 shards, against 306 crate pulls and no guarantee at all.
Which route fits your account
| Your situation | Best route | Reasoning |
|---|---|---|
| Below level 25, no Lab | Farm Coins and XP in standard mode | The Lab and fusion slot are both hard-gated; nothing else you do matters yet |
| Level 25+, no Mythic in the Index | Pull one cheap Mythic from the standard crate first | The fusion slot requires a Mythic already registered |
| Already holding a Golden Brainrot Seed | Fusion with catalyst | 400 shards protects a seed worth ~17 raid clears |
| No seed, large shard balance | Crate pulls to pity, or buy the seed from a trader | Pity at 200 pays a random Mythic, so it is not a Caylus guarantee |
| Returning after a long break | Convert legacy essences at the Lab vendor | Old Alchemy Essences convert 1:1 and many players never notice they are still banked |
If Caylus doesn’t appear: causes, checks, fixes
| Symptom | Likely cause | Fix |
|---|---|---|
| Fusion animation completes, no unit | Reward routed to Lab storage | Open Lab → Storage and claim manually |
| Recipe slot rejects materials | Item has an active trade lock | Wait out the lock timer, then reinsert |
| Lab button greyed out | Questline incomplete or event ended | Finish Lab Rat part 3, or wait for permanent Lab mode |
| Got a different Mythic from the crate | Pity system paid out | Pity gives a random Mythic, not Caylus specifically |
| Progress bar stuck near completion | Server desync | Rejoin a different server; the state is server-side |
Work through these in order rather than jumping to a support ticket. The two most common reports are storage routing and trade locks, and both are self-fixable within a minute. Trade locks are the one people miss most: a material received in a trade cannot be consumed by the Lab until its lock expires, and the recipe UI shows the item as present but refuses it without explaining why.
If the fusion genuinely failed at a 70% rate and consumed your materials, that is working as designed, not a bug — the catalyst exists precisely to remove that outcome. Before contacting support, note the fusion timestamp, your Lab level, and whether a catalyst was active; those three details are what determines whether a rollback is possible.
Frequently Asked Questions
Is Caylus permanent or event-only?
Per the current patch notes, Caylus stays in your account once obtained, but the fusion recipe itself is tied to the Alchemy Lab being available. When the Alchemy season ends, the Lab typically shifts into permanent mode and the recipe stays live. During transition weeks, the Index is the authoritative source for whether the fusion table or the crate pool is the active route.
Can I just trade for Caylus instead of farming it?
Yes, if trading is enabled for Mythic units in that patch and you have the currency. Trading is the only route with a guaranteed outcome and no randomness, but the price is set by players and moves with supply, so it is usually the most expensive option in raw Coins. For most accounts, fusion with a catalyst is cheaper than the market rate.
What is the cheapest route to Caylus?
The Lab fusion with a catalyst is the cheapest guaranteed route: 3 guaranteed raid clears for Alchemy Essence, roughly 17 expected Hard clears for the Golden Brainrot Seed, 2,500 Coins for the Rainbow Sprout, and 650 Sun Shards for the fee and catalyst. The crate route can theoretically cost one pull at 250 shards, but a 90% confidence level costs 306 pulls and 76,500 shards.
Does the crate pity system guarantee Caylus at 200 pulls?
No. The pity counter at 200 pulls awards a random Mythic from the current pool, and Caylus is only one entry in that pool. Pity guarantees a Mythic, not a specific Mythic, which is the main reason the crate is a poor target for a single unit. Treat pity as a consolation rather than a plan.
What level do I need for the Alchemy Lab?
The Lab build option unlocks at account level 25, but the fusion slot that actually crafts Caylus requires the Lab at level 3 and the Lab Rat questline completed through part 3. Players who hit level 25 and build immediately still see a locked slot, which is the questline gate, not a level gate.
Is Caylus worth building around?
Caylus is a support unit, so its value depends on your other plants rather than on its own damage. It performs best in endless and raid setups where adjacent units can carry the damage, and it is close to wasted in short normal-mode waves where the buff window never pays off. If you mainly run quick clears, spend the materials elsewhere and revisit Caylus when you push endless.
